From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BCCD3C77B75 for ; Mon, 8 May 2023 17:41:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233057AbjEHRlt (ORCPT ); Mon, 8 May 2023 13:41:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48562 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232416AbjEHRlr (ORCPT ); Mon, 8 May 2023 13:41:47 -0400 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8E7791722 for ; Mon, 8 May 2023 10:41:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1683567706; x=1715103706; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=bZxp8T48RVcCKdy1tvjKU15d/nNmbsQ40mQ+QrX4vTg=; b=FAQ40P8Mu42WF+EMci91bez88w05DZFEnraKdjMU3Q+0p5jyHE8ZX27r /hiD5Em8k3c1iIXqqQKE3C1jBGmlLlS8/Jzp2raQZ/0ZjDKdYSmCyvC8p gtU/qfn6AdZTX15/CnikbW2dB5CxLGnimRZlkfhdxgl5ayES8dnvm0w/7 FmdPJQKhdTzg7O2NTN1kSRjSNSH5tl79v94W4eJ/CyzI+7P2UyoybGt8B fBmmxIZx3zMsbHTLG0CXGD3VknjypP19JP9NUwABykeRujkz0GQ5BjwZo 39VhFqlfz1GgllEBUsK5Dr+m5MAzp4Ojg+RrV1DayrBkQF1B8qa9HNbSA w==; X-IronPort-AV: E=McAfee;i="6600,9927,10704"; a="436032806" X-IronPort-AV: E=Sophos;i="5.99,259,1677571200"; d="scan'208";a="436032806" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 May 2023 10:41:46 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10704"; a="944946196" X-IronPort-AV: E=Sophos;i="5.99,259,1677571200"; d="scan'208";a="944946196" Received: from turnipsi.fi.intel.com (HELO kekkonen.fi.intel.com) ([10.237.72.44]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 May 2023 10:41:44 -0700 Received: from kekkonen.localdomain (localhost [IPv6:::1]) by kekkonen.fi.intel.com (Postfix) with SMTP id 70C611203DA; Mon, 8 May 2023 20:41:42 +0300 (EEST) Date: Mon, 8 May 2023 20:41:42 +0300 From: Sakari Ailus To: Tomi Valkeinen Cc: linux-media@vger.kernel.org, laurent.pinchart@ideasonboard.com, bingbu.cao@intel.com, hongju.wang@intel.com Subject: Re: [RFC 3/7] media: uapi: v4l: Document source routes Message-ID: References: <20230505215257.60704-1-sakari.ailus@linux.intel.com> <20230505215257.60704-4-sakari.ailus@linux.intel.com> <5b7038ce-d897-931f-2c6e-30bdd1a30342@ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Moi, On Mon, May 08, 2023 at 07:35:04PM +0300, Tomi Valkeinen wrote: > On 08/05/2023 19:26, Sakari Ailus wrote: > > Moi, > > > > On Mon, May 08, 2023 at 01:33:24PM +0300, Tomi Valkeinen wrote: > > > On 06/05/2023 00:52, Sakari Ailus wrote: > > > > Document how internal pads are used on source routes. > > > > > > > > Signed-off-by: Sakari Ailus > > > > --- > > > > .../userspace-api/media/v4l/dev-subdev.rst | 18 ++++++++++++++++++ > > > > .../media/v4l/vidioc-subdev-g-routing.rst | 5 +++++ > > > > include/uapi/linux/v4l2-subdev.h | 6 +++++- > > > > 3 files changed, 28 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/Documentation/userspace-api/media/v4l/dev-subdev.rst b/Documentation/userspace-api/media/v4l/dev-subdev.rst > > > > index a4f1df7093e8..395e06d2f0f2 100644 > > > > --- a/Documentation/userspace-api/media/v4l/dev-subdev.rst > > > > +++ b/Documentation/userspace-api/media/v4l/dev-subdev.rst > > > > @@ -551,6 +551,24 @@ A stream at a specific point in the media pipeline is identified by the > > > > sub-device and a (pad, stream) pair. For sub-devices that do not support > > > > multiplexed streams the 'stream' field is always 0. > > > > +.. _v4l2-subdev-source-routes: > > > > + > > > > +Source routes > > > > +^^^^^^^^^^^^^ > > > > + > > > > +Cases where a single sub-device pad is a source of multiple streams are special > > > > +as there is no sink pad for such a route. In those cases, an internal pad is > > > > +used as the sink pad. Such pads have the :ref:`MEDIA_PAD_FL_INTERNAL_SOURCE > > > > +` flag set. > > > > + > > > > +Internal pads have all the properties of a sink pad in such case, including > > > > +formats and selections. The format in this case is the source format of the > > > > +stream. An internal pad always has a single stream only (0). > > > > + > > > > +Generally source routes are not modifiable but they can be activated and > > > > +inactivated using the :ref:`V4L2_SUBDEV_ROUTE_FL_ACTIVE > > > > +` flag, depending on driver capabilities. > > > > + > > > > > > I find the above chapter a bit difficult to read, but I think we need to > > > conclude on the internal-pad vs internal-source-pad discussion first. > > > However, one point/question: > > > > > > You write that there's only one stream in an internal pad. I wonder if > > > that's a good or a necessary limitation... Do you see that allowing multiple > > > streams brings extra complexity? It's still up to each driver to decide how > > > many streams they support (most would just support a single one), so each > > > driver can easily enforce that limit. > > > > Good question. As we don't seem to have a tangible reason to allow it, I'd > > deny it until there's a use case. > > > > Or did you have a use case in mind? > > > > I thought indicating which streams will be bound together (i.e. either are > > all disabled or enabled) could be one, but I'm not sure we need that at the > > moment at least. > > I don't have nothing concrete in mind. Maybe a TPG which also generates some > kind of metadata. But that could be implemented as two internal pads. > > > > I'm fine with starting with only single-stream support, but if we later need > > > to loosen that restriction, I wonder if it'll be difficult if we have > > > specified that there can be only one stream. I.e. will the drivers and the > > > userspace depend on that limit. > > > > We can always allow what wasn't allowed previously so that's a non-issue, > > really. But it needs to bring new functionality, otherwise there's no > > reason to do that. > > It's not always that easy. If the drivers and the userspace expect that > there's a single route with ID 0, and then with a new kernel there are more > streams or the single stream is ID 1, things could go wrong. Other drivers are a non-issue IMO as this isn't visible to other drivers. I think for user space this could be an issue if it were entirely generic. But that's probably not going to be the case, is it? I don't mean test programs. -- Terveisin, Sakari Ailus